In an emergency of a vehicle, a seat belt device stops paying out of a seat belt by means of a retractor. Furthermore, a pretensioner provided in the seat belt device pulls the seat belt. At this time, the pretensioner moves a piston in a cylinder to pull a wire with the piston, using gas generated by a gas generator. By pulling the seat belt with the wire, the seat belt is tightened. An occupant is restrained to a seat by the seat belt and is protected.
In a conventionally known pretensioner, a piston moving in a cylinder pulls a wire attached to a seat belt (see PTL 1).
In such a conventional pretensioner, one end of the wire is inserted into a hole in the piston and is fixed to the piston by a tubular wire end. At this time, by crushing the wire end, the wire end is fixed to the end of the wire. When the piston moves, the wire is pulled by the piston, and then pulls the seat belt.
When the pretensioner is activated, the wire needs to be reliably secured to the piston by the wire end. To achieve this, by increasing the length of the wire end (a portion to be crushed), the wire end is securely fixed to the end of the wire.
Therefore, in the conventional pretensioner, the length and weight of the piston, including the wire end, tend to increase in response to an increase in the holding power of the wire. Furthermore, because a length of a portion of the wire to be fixed to the wire end increases, the weight of the wire also increases. As a result, the cost of the pretensioner increases, and the weight of the pretensioner increases.
Furthermore, in the conventional pretensioners, typically, a gas generator generates high-temperature, high-pressure gas. In order to deal with this gas, the gas generator is accommodated in a thick-walled, heavy pressure container and is fixed to the pressure container by a cap. The pressure container is securely fixed to an end of the cylinder so as not to leak the gas. Furthermore, a base that supports the wire is fixed to the pressure container. The base is made of a strong, heavy member and is fixed to the pressure container with screws or by crimping.
Like this, the conventional pretensioner is made of a plurality of components including heavy components and components that are difficult to handle. These components of the pretensioner are machined (for example, screw machining) for fixing. By sequentially fixing the plurality of components with screws or by crimping, a pretensioner having a complex structure is assembled. Due to this assembly method, the assembly of pretensioner tends to require time and effort. Furthermore, because the assembly of the pretensioner is complex, the assembly man-hours and the cost of the pretensioner increase.
To counter this problem, a pretensioner that is composed of a reduced number of components by using a base cartridge having a plurality of functions is known (see PTL 2).
However, because the base cartridge is large and heavy, the handling of the base cartridge is difficult. Because this base cartridge needs to be fixed to a cylinder, the assembly of the pretensioner requires effort. Furthermore, similarly to the above, a gas generator is fixed to the base cartridge with a cap. Thus, the conventional pretensioner requires machining for fixing and complex assembly work, and, due to the complex structure of the base cartridge, the structure of the pretensioner also becomes complex.